Starship is Go...

Oldfart1939 · 2024-10-13 13:26:36

I was up at 05:30 MDT and watched the entire flight.
But for those here who were still snug in their beds, I've subsequently watched several rehashes and selected one by Scott Manley to post here. NO annoying AI voices!!

https://www.youtube.com/watch?v=Ysx4t7ICO58

Enjoy! I finally am feeling confident that we may reach Mars in my lifetime!

Void · 2024-10-13 18:00:17

It was good, OF 1939.

I think it was a big win of a gamble to get a Superheavy back just dinged up a bit. I am going guess they can improve future versions.

If I am not mistaken, did they use Raptor 2's in this launch?

I think they should consider trying to get a Starship back from orbit using the peg legs. They did succeed once.

Not that the tower idea is a bad one, but it seems the Starship got pretty messed up even this time. If they had one to do forensics on that could be a big help before they test the tower with a Starship.

I would be imaging they might be able to land one on a military base, so that there would be less of hostile interference methods employable.

On a Military base the ship could be examined and taken apart, as it is not likely to be reused.

And a crash event would be harder for the enemy to exploit.

And they are going to have to land Starship on legs on the Moon and Mars anyway, at least at first.

Ending Pending

Last edited by Void (2024-10-13 18:06:47)

tahanson43206 · 2024-10-13 18:55:12

For Void ....

I don't know the answer to this question... I am picking up on your suggestion to consider chopsticks for Starship.

Do you know what the development plan might be? The Google Meeting participants seemed to think a land landing for Starship might be next.

(th)

kbd512 · 2024-10-13 22:56:23

SpaceX's original 450 to 500t "Starship" design was the correct size for what they're attempting to do. Elon has already stated that he thinks Starship will be amongst the smallest of rockets in the future. For any serious colonization efforts, we need larger rockets launched from floating offshore platforms not subject to FAA launch permits.

This was Boeing's "Space Freighter" concept:

It's approximately the correct size, and also a fully reusable TSTO. I think it had lots of potential, but the political games surrounding the Space Shuttle design killed the concept. The booster was to be powered by LOX/LCH4, much like Starship. This is what NASA really wanted, and it's pretty easy to understand why. A shuttle of that size enables many different kinds of mission and is large enough to function as a mobile base or space station. Starship has approximately the same internal pressurized volume as ISS, around 1,000m^3 for both. The Space Freighter could have around 9,946m^3 of pressurized volume in the form of a payload bay (18.5m diameter by 37m length) module. Even if it were slightly smaller than that, it's a staggering amount of usable internal volume. The AN-225 had 1,100m^3 of internal volume for comparison purposes, so very similar to Starship. This is enough volume and mass transfer potential to do real missions inside the inner solar system. Using composite materials, I think it's accurate to assert that internal cargo volume could be doubled. SpaceX actually built 17.5m diameter composite tanks before abandoning that project a bit too soon, in my estimation.

This is approximately what I initially envisioned a "Starship" to be:
T0002up.jpg654cd85f-e442-41f6-9fea-c1bc595abdcaZoom.jpg

It's a modestly aerodynamic "surfboard" upper stage which could land on a convetional runway, so as to use the existing spaceport infrastructure around the US. We built a number of ridiculously long runways for a reason.

Eliminating the wings and landing gear from the booster by cacthing the booster just above the ground using "Mechazilla" was a stroke of genius, but I feel as though a fixed delta wing configuration orbital vehicle eliminates the shock impingement heating or gas bleed-through issue that I don't think is readily solvable if they persist with the moveable "body fins" attached to Starship, or whatever SpaceX is calling them. I could be wrong. There could be a simple and elegant design that solves those problems, but I don't know what that would be. Whatever they've attempted up to this point, it still hasn't solved that problem. The "burn through" occurs because they've either created a stagnation point at the attachment point near Starship's body / propellant tanks, or hot gas from the windward side of Starship is bleeding through that gap, however small, until it starts removing pieces of the vehicle.

Perhaps there's some sort of conformal hinge cover they can fabricate to seal the gap, but a lifting body that lands on a conventional runway would be no heavier than all the propellant Starship must hold in reserve for vertical landing. Wings provide aerodynamic lift and stability, greatly increase cross-range, and it's possible to shield the control surface attachment points from the oncoming flow. Starship and its giant fins are already covered with heat shielding tiles, so none of those have been eliminated using their all-steel design. Starship is much larger than the Space Shuttle Orbiter, so it has even more tiles. However, we have much better materials now that weren't available or tested to perfection during the Space Shuttle program.

Void · 2024-10-14 08:37:28

I would think that over time there may be a further return to wings, maybe starting with Dream Chaser and then sizing up. But that is for Earth, maybe someday for Venus.

Marcus House: https://www.youtube.com/watch?v=NwR6caqf8GA
Quote:

SpaceX Starship Flight 5 Catch Explained! Yes, finally it happened!
Marcus House
544K

Sounds like new versions of Starship will have forward flaps modified which could help.

The fire at the side of the Superheavy was simply venting to make the booster safe.

Some engines got warped, that is not good, but yesterday I heard chatter that Elon Musk does not think that that is unsolvable.

Maybe, as M. House has said they could do a true orbit for Starship and try landing it next time. I am not sure that the Starship has the needed modifications for a tower landing yet though.

I think it would be really interesting to see a try to land on Peg Legs.

Ending Pending

Last edited by Void (2024-10-14 08:44:09)

Oldfart1939 · 2024-10-14 10:49:33

In reply to post #1904, there are several airports that have very long runways in the Western US; one which I am intimately familiar with is in Casper, Wyoming. Ii's around 11,000 feet long and was originally built by the US Army Air Corps during WW 2 for teaching rookie pilots to fly and operate both B 17 Flying Fortress bombers and B 24 Liberators. The only problem that I would see for using it to operate space planes is something known as "Density Altitude." During Summer months, it's difficult to get small and low powered aircraft airborne. The field is at 5,350 feet above MSL, and Summer temperatures can reach into the mid to high 90's. Density altitude is a function of temperature and extends the landing and takeoff performance of all aircraft, making the operating altitude something like 9,000 feet above MSL.

As an aside, Chuck Yeager trained there learning to fly the P 51 Mustang

GW Johnson · 2024-10-14 12:18:20

For "Starship" to land on Earth, it either needs landing legs or to be caught by the tower, or else wings to land aerodynamically on a runway. I've seen things indicating SpaceX wants to catch it with the tower.

For "Starship" to land on the moon, it has to have landing legs, and they cannot be the little "peg legs" the early single-stage flight tests used. Landing on the moon is a soft field, rough field problem. The max allowable static bearing pressure is about 0.1 MPa. And the cg height is way too high for anything resembling the "peg legs" to be stable against overturn. There are no towers or hard landing pads on the moon. There won't be for a long time yet.

For "Starship" to land on Mars, it has to have landing legs rather similar to those it has to have on the moon. That atmosphere is way too thin for wings to be of any use at all. There are no towers or hard landing pads on Mars. There won't be for a long time yet.

All that being said, I think there might be a solution to the hinge line burn through problem. That would be a flap of flexible heat shield material (perhaps a ceramic blanket?) extending from inboard across the hinge line to a bit outboard, on the windward side of the fin. The pressure is dropping in that direction, so there cannot be backflow under this flap of material toward the hinge line. But it does need to be impermeable.

Combine that with the right legs, and you have a solution for the moon, Mars, and for off-site abort landings on Earth.

GW

Last edited by GW Johnson (2024-10-14 12:20:57)

kbd512 · 2024-10-14 12:41:36

Void,

The engines on the Space Shuttle didn't "warp during flight" because the entire body of the Orbiter vehicle was blocking the oncoming hypersonic flow. This was possible because the Space Shuttle had large delta wings to provide aerodynamic lift. You don't need any aerodynamic control surfaces to land on the moon, because they're useless dead weight in the vacuum of space. You need radically different and much larger control surfaces to land on Mars, because the atmosphere at Mars Sea Level is the same as Earth atmosphere at about 130,000ft. Like it or not, there is such a thing as an appropriate aerodynamic design for the environment you're designing the vehicle to operate within. This is simple immutable flight physics, not subject to beliefs or aesthetic preferences. You might be able to solve some problems using brute force, but soft landing is not one of them.

If you create a swept wing airliner design intended to fly at 150mph, then by definition of the flow characteristics over its wings, it's highly sub-optimal for flying at such a low speed, which is why nobody who pays more attention to flight physics than aesthetics designs an airliner to fly that way. The wings of a jet airliner are "swept back" because the aerodynamic drag associated with a "Hershey bar" wing design intended to fly at 650mph vs 150mph would be horrendous. A swept wing airliner can still remain airborne at 150mph, just barely, but only after deploying multiple lift-enhancing devices (such as fowler flaps, slats, and increasing angle-of-attack) that add a considerable amount of drag and increasing engine output to compensate. Airliners with swept wings and hi-bypass turbofan engines are optimized to fly well at 30,000ft to 40,000ft at around 650mph, but not at any other flight speed or altitude. In every other regime of flight, they're either at the edge of their flight envelope or wasting a lot of fuel merely to remain airborne. That's why the very first thing they do after takeoff is to climb for the heavens. If they don't operate that way, then they will never achieve the range and fuel economy they've been optimized for. Their turbofan engines are likewise optimized to fly at specific cruising speeds and altitudes. If you're going to fly slower than 400mph or below 30,000ft, then turboprop engines are going to provide substantially better range, economy, and endurance. If you're going to fly at 350mph or slower, then piston engines and conventional propellers are going to burn a lot less fuel than turbofans or turboprops. There's no "engineering magic" to skirt around this, merely highly consequential design trade-offs and optimizations.

So...

If Starship had a fixed-geometry delta wing, then its engines and control surface attachment points would not be subjected to extreme heating from hypersonic flow, because that flow would be blocked by the structure in front of it. It's a problem that wouldn't need to be solved, which means SpaceX could instead focus on solving all the other design challenges which are inseparable from high performance aerospace vehicles. This was a problem of their own choosing, and it doesn't seem as if they clearly understood either the severity of the problem or what an actual fix would entail. They definitely made significant changes to the body flap design, but there are still chunks of the vehicle flying off during reentry.

After aesthetics and personal beliefs are subordinated to results, there's a reason all working design solutions look so similar. There are a finite number of optimal solutions, and they look the way they do because that is what the flight physics demands of the design. When the Soviets designed Buran, the reason it looked like our Space Shuttle was that they wanted it to do what our Shuttle did, but "better" by their own definition. The striking similarity fulfills the same cross-range, payload, and other mission requirements. They thought our Space Shuttle had a specific military purpose, and it did, but it wasn't a militarily useful capability, which they recognized before we did. They still had a militarily heavy lift rocket (an all-liquid SLS equivalent) after the Buran program was terminated, but then decided that wasn't required, either.

We use lifting bodies for reentry vehicles because that is the one design which provides maximal lift and acceptable control authority over all phases of flight. Similarly, control surfaces that must function well across subsonic, supersonic, and hypersonic flight tend to be grid fins because that particular design provides maximum control authority with minimal stress on the attachment points. It's not a matter of personal preference. If you throw enough money at a given flight physics problem, then you can probably devise something minimally functional, but it will never be as cost-effective, reliable, and lightweight as it could be if it was optimized to do what it must.

The tradeoff for attempting to land a Starship at a launch tower is that it's incapable of landing anywhere else. It's going to topple over and explode if it cannot be captured. This is an acceptable risk for an unmanned booster stage where the weight and cost benefits of air capture outweigh the negative consequences of a failure. Airliners don't attempt vertical landings, even though we could entirely eliminate those expensive runways, because the dangers and design compromises are so great as to make that tradeoff "not worth it" in the eyes of virtually all airliner designers. It's not a case of nobody ever having tried or thought of it before. We did try, and it was mostly a better than average way to get people killed. After decades of experimentation, we reached the conclusion that using a runway is not a major impediment to the operation of useful jet airliners. KSC has a very long runway, and that's where SpaceX ultimately wants to launch their Starship from, so they may as well use it. A simple tow truck can return their upper stage back to the pad. The time imposition is minimal. There are also numerous viable alternative runways around the world to choose from. Having landing options is a good thing, even if you don't intend to use them during normal operations. If they design-in detachable pylon structures to mount a couple of turbofan engines, they can fly Starship back to the launch site after an emergency divert.

The ability to burn all the propellant in the upper stage is going to do more to offset the dead weight of wings, in terms of payload performance, than a vertical landing capability without landing gear. This becomes readily apparent as you attempt to scale-up, in terms of payload performance. The visual depiction is merely a concrete example for visual people to use as a reference concept. It's definitely not me saying, "this is the exact correct design to use." I only know that "the correct design" is a lifting body rather than a cylinder with marginal pitch stability and roll control authority.

tahanson43206 · 2024-10-14 12:49:02

For kbd512...
You keep arguing for wings, and all your arguments seem (as I read them) to make sense, but no one appears to be buying what you're selling. People are risking ** real ** money (in the billions of USD or Yen or whatever) to avoid wings like the plague.
What are all those people missing that you see so clearly?
(th)

kbd512 · 2024-10-14 13:01:00

GW,

We're talking about 3 different vehicles subjected to 3 different landing conditions with very different design requirements. Using wings at Mars isn't about providing "up force" below supersonic speeds, so much as arresting the vehicle's rate of descent. The two nuclear powered rovers we sent there both used heat shields designed to generate aerodynamic lift to do that. Rocket propulsion will have to be used to soft land on Mars, as well as on the moon (obviously). If the vehicle is to ever return to Earth, then it must have a heat shield, and a fairly substantial one at that. Since SpaceX's plan is to return their vehicles to Earth, or at least some of them, then it would make sense to use aerodynamic lift to do that.

kbd512 · 2024-10-14 13:21:14

tahanson43206,

Great! Let's ignore basic flight physics in favor of blind ideology. That always works so well.

We've never learned anything from past mistakes before, so why should this time be any different?

On the off-chance that someone else here is not blind, let's get a good look at those 4 giant delta wings on Starship:

Those are clearly not "wings", they're "fins"!

Calliban · 2024-10-15 00:02:27

I have to admit, I was sceptical about the chops sticks idea of catching the super heavy booster on decent. It looked to me like it would result in heavy point loads on the air frame. It also requires very precise alignment to be able to work. But they tested it and it did work. Well done SpaceX!

Void · 2024-10-15 07:27:11

As I understand it the Raptors can hover in Earth's gravity field which gives time.

Merlin's cannot hover, so they have to time the engine cut-off and so do a Hover-Slam.

Also with computers the reaction times are likely to be much better than humans.

If they can factor in the environment such as wind, etc. And the Superheavy is healthy it seems that they can do it.

They can study the recovered booster to perhaps improve it's fitness.

And then it becomes a question of how many times they can recover the Superheavy, and what damages may occur with an unhealthy Superheavy or tower.

I think that the new versions will have the raptor 3 eventually. I think these were 2's.

I think the dream is to use a Superheavy three times a day, to launch 3 Starships. That would be quite a lot, I expect that to happen in Florida, or offshore.

They will want lots of towers so that on a mishap or need of repairs they can shift the launch towers.

Ending Pending

Last edited by Void (2024-10-15 07:31:51)

kbd512 · 2024-10-15 10:52:44

My point about this is rather easy to understand. SpaceX already has gigantic wings attached to their Starship. We can be as obtuse about what we're looking at in the photos of Starship as we want to be, but that doesn't actually change reality. SpaceX could increase the volume of those wings by just a little bit, and then they have a proper delta-winged lifting body capable of glide-landing on a runway.

In a horizontal propulsive landing configuration, only 4 of those dual-engine SuperDraco thrusters are required to soft-land a 250t Starship on the moon in a horizontal attitude. If you have 2 pairs of engine clusters per corner, then you have reserve thrust to spare, and they can throttle from 20% to 100%. Starship landing on it's belly is substantially more stable than it is when vertical. Those engines might weigh 50 to 100lbs per pair. It has to have a reaction control system anyway, in order to control its attitude on-orbit, and thus far SpaceX uses NTO/MMH thrusters on all of their Dragon capsules. They require new control software, but not new engines or operational techniques. Horizontal propulsive (moon and Mars) and glide landing (Earth only) solves many more problems than it creates.

I'm not talking about landing Starship's booster this way, only the portion of the vehicle containing humans. If you ever mess up a capture attempt, then you kill everyone on board, because the vehicle crashes and explodes. There's at least a chance of survival with a slightly botched glide landing, coming back with empty propellant tanks and using aerodynamic lift to "fly". There is no chance of survival at all if Starship either misses the capture arms, runs into the tower, or an engine fails during hovering. Every landing has to be a perfect landing, or everybody dies.

This is a rather simple proposition to me, and not about what I'd rather have. A propulsive vertical landing "looks way cooler" than gliding onto a runway, but it's also very dangerous and must be executed perfectly every time. It would be highly hubristic to suggest that no combination of reentry thermal damage, atmospheric effects, engine or propellant feed or control software failure, would ever result in loss of crew and loss of vehicle. Maybe the tower / pad infrastructure is now hardened to the point where that won't be lost.

Ask yourself how comfortable you are putting the lives of your children in the hands of all the main propulsion systems and control software which enables a vertical landing, versus a pilot who can land a Space Shuttle. No Space Shuttle was ever lost during a landing attempt. Why would there be? The Orbiter's flight control system included multiple built-in redundancies because it was mass-effective to have those redundancies, there were two ace pilots at the controls who had practiced thousands of landing attempts in both simulators and a real flying simulator, and the systems which enabled landing were dramatically simpler than the systems controlling the main engines.

Rapid refurbishment comes down to the durability of the heat shielding materials and propulsion systems, for both the Space Shuttle and Starship. The Space Shuttle was our first attempt. The basic design concept wasn't "wrong", it was subject to the materials and design limitations of that era. 2025 is half a century removed from 1975. The systems we have today are much more durable, lighter, and reliable, but the same operational limitations clearly still apply.

After you fire the main engines, inspection and refurbishment are required. After you reenter, heat shield inspection and refurbishment are still required. Using a horizontal landing to scrub velocity and storable chemical propellants for a propulsive soft landing (where required), you only have to successfully fire the main engines once per flight segment before you're back on the ground, whether on Earth, the moon, or Mars. That is a completely workable operating methodology. It's proven to work and does not demand even more extreme performance from the main engines or heat shield. If the main engines were damaged from ascent or reentry heating, then you get to figure out what to do about that on the ground where time and repair options are far more accessible than they are during flight.

Is that overly-conservative engineering?

Possibly, but far fewer people have died from reduced complexity operations. You fire the main engines and achieve orbit. Great. That part of the flight worked. Before their next scheduled safety-of-flight critical firing, the engines get inspected for damage and repaired, if required.

If and when we have the engines, plumbing, software control systems, and landing sequence so thoroughly sorted out that vertical landings no longer present a major technical risk to successful flight operations, then we can save even more mass and cost by transitioning to VTOL mode of operation. The vehicle is still perfectly capable of doing that, even with its pair of wings. If that takes longer than anybody iniitially thought possible, it won't become an impediment to execution of the exploration and colonization programs. I think fantastic progress has already been made towards that end. Proclaiming its reliability on the basis of a single successful test flight is very premature. We're working with a single data point. I want to know how many crashes of either the Super Heavy booster or Starship we'll experience over 1,000 flights. If launch cadence dictates flying once or twice per day, then we'll have an answer to that question in the next 3 years or less.

This is merely an option that presents very low technical and operational risk. A gliding landing using a lifting body is a known approach to vehicle recovery that's proven to work over decades of flight experience. It may not be 100% optimal, but the problems and solutions are known to us with a very high degree of certainty.

Falcon 9 first-stage boosters landed successfully in 355 of 367 attempts (96.7%), with 330 out of 335 (98.5%) for the Falcon 9 Block 5 version.

Losing 15 Starships over 1,000 flights is an unacceptable loss rate. If we lost airliners at that rate, nobody would fly. Loosing 15 out of 1,000 boosters is simply the cost of doing business. Vertical landing is intrinsically hazardous because the error margins are so vanishingly small. The accident rates for helicopters are, in general, significantly higher than for fixed wing aircraft in similar weight categories. In contrast, SpaceX's reliability rate for launches is near-perfect. There were 2 in-flight failures over 394 flights spanning 14 years of Falcon 9 operations, with no repeat in loss mechanisms. I know one of them was a high pressure Helium tank bursting in the upper stage. I think the Starlink loss was a LOX leak. Now that we're going to start flying once per day, total operational complexity and loss mechanisms and probabilities matter quite a bit more to the FAA not grounding the vehicles.

Anything you do during normal course of business has to be exceptionally reliable. Losing 5 Starships per year is not going to inspire confidence in the vehicle or mission. Space flight has always been fraught with hazards, but surviving a launch, a mission, and a reentry, only to be blown up while attempting to land is not going to sit well with anybody. FAA absolutely WILL have something to say about that. Either VTOL reliability improves quite a bit over the actual Falcon 9 booster landing success rate, or the entire notion of vertical landing crewed vehicles will be called into question. Maybe they run Falcon 9 boosters on the ragged edge of the margins, and that explains the loss rate, but I think the more likely answer is that it's an intrinsically more hazardous method of landing than gliding back to Earth with empty propellant tanks.

Void · 2024-10-15 11:12:22

Down the line, I expect someone will build a large, winged device to accommodate large numbers of humans landing on Earth.

But for now Capsules and Dream Chaser can bring people down, and that will get us back into a winged passenger service.

But Starship/Superheavy is going to be a cargo carrier for the most part for the first few years, until they demonstrate good numbers for safety.

I think it would make lots of sense to send a Starship destined to carry people to Mars up without people on board.
Then when ready load people on board, perhaps. Initial flights to Mars will be no crew or a small amount of crew.
Wings are perhaps not useful on Mars or for Phobos and Deimos.

But I agree, after they get the early versions done they may want to look into wings for use on Earth.

Ending Pending

Last edited by Void (2024-10-15 11:21:25)

Oldfart1939 · 2024-10-15 21:06:57

Here's the link to another video from Fraser Cain, in which Marcus House and Scott Manley combine with Fraser to dissect the entire mission in great detail. A great compilation of footage is included. Oven an hour long, but is the definitive post flight video.

https://www.youtube.com/watch?v=Flv1W6AR-cU&t=15s

tahanson43206 · 2024-10-16 09:31:52

A new (to me for sure) analysis of the recent Starship flights showed up on my Internet feed this morning.

It took a less optimistic view of the landing than the video that Oldfart1939 showed us...

In this video the presenter argued that the burn through during descent caused the explosion of the Starship before it entered the water.

I am doubtful this interpretation is correct, because the Cain video offered the opinion that the Starship video included underwater footage.

However, I though it is worth bringing this Debbie Downer interpretation to the forum so it can be analyzed.

the video showed up on my smart phone while I was trying to do something else so I made no effort to determine the URL.

(th)

Oldfart1939 · 2024-10-16 10:10:29

As a side note, the YouTube presentations boil down to two types: live presenters and AI generated clickbait. Tim Dodd (Everyday Astronaut) is possibly the best of all the live presenters, followed by Felix Schlang (What About It), and then a few others on NSF (Nasa Space Flight). Scott Manley and Marcus House are both top notch, along with Fraser Cain. Most of the others have AI generated voices mispronouncing key words that simply drive me nuts. Other decent presenters are Ellie in Space, and the Angry Astronaut, although Angry Astronaut has become obsessed somewhat with UFO's and aliens, recently. The live presenters are mostly very well informed and knowledgeable. The click bait AI is hard to avoid, but with all the info available now, one has to become more selective to manage one's time spent websurfing,

tahanson43206 · 2024-10-16 10:38:26

For Oldfart1939 re #1918

The voice I heard in the video reported in #1917 was indeed likely to have been AI generated, although it was of a very high quality, so difficult to confirm.

My guess is that a human editor is involved in production of such video's as you described.

Regardless of the source of the question, I think it is worth while for NewMars members to attempt to find out if the explosion of the Starship occurred before the ship entered the water, or after. My impression is that the explosion occurred ** after ** the ship entered the water. On the ** other ** hand, the possibility ** does ** exist that there was a fire on board the Starship in the moments before the landing.

Presumably SpaceX knows exactly what was happening in and around the ship at every stage of the flight.

GW Johnson has published an idea to protect the flap hinges, and I have it on my todo list for today to post here.

The work is already published at exRocketman blog if anyone is in a hurry to see it.

(th)

tahanson43206 · 2024-10-16 17:31:47

And here is an image showing GW's recommendation for a cover over the hinges for Starship flaps....

(th)

GW Johnson · Yesterday 14:25:58

The notion for the sketch in post 1920 is a flexible blanket bonded to the fairing, and lapping over freely onto the fin, held in place by the wind pressure despite sliding effects, while being flexible enough to stay on the fin as it moves. The hinge line is at the tip of the fairing.

I could not think of a reusable material that is both flexible and capable of turning away near-stagnation heating, which is visible as the glowing shocked layer under the fin in the entry videos. Key was to lap over far enough onto the fin so as to prevent backflow from getting under the blanket, by the simple expedient of putting its downstream edge sufficiently far downstream that the pressure there is much lower than the pressure at the hinge line itself.

So, I combined a couple of layers of ceramic fire curtain cloth with an ablative polymer, one loaded with the right solids so that there is significant char layer retention against fluid shear force effects. Most ablating polymer do not have that char retention ability, but the one I specified does. That selection is just a start-point for the proper development of this item. It will have to be tested and verified, before you trust it. But the item is small enough, and easy enough to fab and install, that it would be a small part of the refurb cost to fly again. We're talking about less than about 40-50 square feet of stuff, not a whole "Starship" heatshield.

GW

Last edited by GW Johnson (Yesterday 14:29:32)

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